Why do RHD single turbo kits sound like crap?

[DCTFox]

I’ve been wondering this for a while. All of the US single turbo kits (DOCRace springs to mind) seem to completely transform the sound of the car and the sound is amazing.

Obviously the US kits don’t fit on RHD cars but I’ve seen a few custom jobs done, and not a single one I’ve seen sounds any different to a stock twin setup (not that the twins don’t sound good, but a good single setup is on a different level).

I can only speculate that this is down to exhaust manifold design but can’t imagine it would be hugely different from the US kits so I’ve never really been convinced. Can anyone shed some light on this?

P.S. before anyone replies “grow up, sound doesn’t matter” shut your pie hole, it DOES matter, otherwise why don’t we all just save up for a Tesla.

 

[rev210]

Nope they sound the same for the same setup/turbo, in australia RHD setups need to pass yearly police inspections or avoid getting roadside police defect notices. If you plumb in the wastegate Vs screamer assuming the same turbo , its going to be way more quiet.
If you really want the spool noise , then send your turbo off for a T51r compressor mod.

 

[DCTFox]

Nope they sound the same for the same setup/turbo, in australia RHD setups need to pass yearly police inspections or avoid getting roadside police defect notices. If you plumb in the wastegate Vs screamer assuming the same turbo , its going to be way more quiet.
If you really want the spool noise , then send your turbo off for a T51r compressor mod.

I’m not talking about spool noise, I’m talking about the actual exhaust note from the engine. The twin setups sound very flat and raspy, similar to the S55; I believe this is mostly due to the fact that the exhaust streams are separated as well as the exhaust manifold design, but most of the single setups I’ve heard sound very smooth and rich, similar to the big single 2JZs or RBs, and I believe this is due to the single flowstream resulting in a more even note.

I’m not convinced having a screamer vs recirculated wastegate makes that difference, but I’d like to hear others’ thoughts on it.

Also if you have a link to any RHD setups that sound like a US setup I’d love to see it (hear it). So far all I’ve seen is the contrary.

 

[The Banshee]

I’m not convinced having a screamer vs recirculated wastegate makes that difference, but I’d like to hear others’ thoughts on it..

Open dumps versus recirc makes a huge difference! As well as removing/replacing cats, resonators, and all the other things we do to the exhaust which could very well be the difference you are noticing. I have heard more than 1 left hand drive raspy single turbo n54. They do exist.

The open dump pipes just blast exhaust directly out of the manifold via wastegate valve. It's quite loud. When you redirect all that exhaust back through the exhaust pipes/cats/resonators you can imagine how different the sound effect can be.

 

[DCTFox]

Open dumps versus recirc makes a huge difference! As well as removing/replacing cats, resonators, and all the other things we do to the exhaust which could very well be the difference you are noticing. I have heard more than 1 left hand drive raspy single turbo n54. They do exist.

The open dump pipes just blast exhaust directly out of the manifold via wastegate valve. It's quite loud. When you redirect all that exhaust back through the exhaust pipes/cats/resonators you can imagine how different the sound effect can be.

Man I hope this is the case. I knew a screamer would be super loud but I didn’t think it would change the note. I guess it makes sense though seeing as it’s coming straight from the manifold and bypasses the rest of the exhaust.

 

[135i2]

My RHD ST is a straight through 4 inch from turbo back but switchable into quiet mode through a modified HMS out the rear. GTX 3584 RS sounds tits on full noise. Its catted and legal.

 

[rac]

Don't see rhd, lhd making any difference to noise. Be some difference between log style, short runner v long runner designs and, catless or catted and twin v single mid section etc. Mine sounds way better than my twins did, but it's subjective. I never liked the tractor type acoustics you get from having 3 cylinders split for a decent length of pipe, especially catless.

 

[DCTFox]

Cheers for the replies guys. Either of you have any clips you can share? I’d love to hear what they sound like.

 

[chrisdfv]

Cheers for the replies guys. Either of you have any clips you can share? I’d love to hear what they sound like.

Doc race cars sound the best period. Myself and 2 other local friends have confirmed this multiple times. I believe is just the design of their manifold. Compared to my Vi engineered manifold, and my other friend's speedtech car. The doc car sounds the most aggressive and IMO has the best exhaust tone. It sounded good even with a stock exhaust. He straight pipped it, and it sounds the same except 100xs louder, but the tone is unchanged.

 

[Rob09msport]

Doc race cars sound the best period. Myself and 2 other local friends have confirmed this multiple times. I believe is just the design of their manifold. Compared to my Vi engineered manifold, and my other friend's speedtech car. The doc car sounds the most aggressive and IMO has the best exhaust tone. It sounded good even with a stock exhaust. He straight pipped it, and it sounds the same except 100xs louder, but the tone is unchanged.

You know it's true when someone says the best isn't what is on their car.

 

[DCTFox]

Doc race cars sound the best period. Myself and 2 other local friends have confirmed this multiple times. I believe is just the design of their manifold. Compared to my Vi engineered manifold, and my other friend's speedtech car. The doc car sounds the most aggressive and IMO has the best exhaust tone. It sounded good even with a stock exhaust. He straight pipped it, and it sounds the same except 100xs louder, but the tone is unchanged.

This was my original thinking. The only thing that really makes sense to me is the manifold design, and the doc kits have always sounded the best from what I’ve seen. My guess has always been that for the custom jobs that have been done for UK cars, the fabricators didn’t put much stock into making sure the tube lengths were all perfectly equal and instead focused on getting the thing to fit.
The DOCRace manifold is a work of art compared to the RHD ones I’ve seen, hopefully they will make a kit for RHD cars at some point. I DM’d them on Instagram to ask but they never replied.

 

[martymil]

Because it cant be made for RHD as theres just no room for a doc race style manifold and a proper dump.

I've helped develop two different kits for RHD with little to no room for anything else but you could easily do a screamer pipe version at your own risk.

 

[DCTFox]

Because it cant be made for RHD as theres just no room for a doc race style manifold and a proper dump.

I've helped develop two different kits for RHD with little to no room for anything else but you could easily do a screamer pipe version at your own risk.

Such a shame, ah well. I’m guessing you are Aussie, there only appears to be one kit on offer in the UK from Walton Motorsport but it’s stupidly expensive and doesn’t produce a particularly nice sound. I’ve seen a couple other custom jobs which didn’t sound any better and were probably more expensive.
Sad that there aren’t too many options for single kits in the UK which just leaves upgraded twins, but from what I’ve read none of the upgraded twin options are particularly reliable long term.

 

[martymil]

Yes I'am from OZ and we tried everything and the final revised kit is of it tits for big hp.

We just finished 93 tuning and next we are going back to e85 to run some numbers but 500rwk on our low reading dyno
is not a problem.

We ran the car on two completely different dynos and the power levels where almost identical +-5rwk.

I personally run the gc2.0 with the upgraded mar-m246 wheels and they have been solid, I made 387rwk on e15, basically 93 with a splash of e for knock control.

Way to much power for street and track use but if your into drags this can be done of straight e85 and turned up to 450rwk plus with the right supporting mods.

Its way more than any stock engine can handle.

Set a realistic goal and stick to it.

 

[Torgus]

Don't see rhd, lhd making any difference to noise. Be some difference between log style, short runner v long runner designs and, catless or catted and twin v single mid section etc. Mine sounds way better than my twins did, but it's subjective. I never liked the tractor type acoustics you get from having 3 cylinders split for a decent length of pipe, especially catless.

Amen. My single turbo sounds 10x better than the twins ever did on the same OEM PE exhaust. Both had no primary cats.

I would assume ACF and DocRace ST or similar top mount twin scroll t4s would sound the same. The doc race has longer runners and sub optimal wastegate placement in terms of manifold design but the screamer pipes and exhaust are all going to sound very similar to ACF etc. vs. twins or a single scroll log manifold. Acf has a 3.5 inch dp vs. Doc race at 3" iirc but that will not change sound really just performance and only slightly. Both I think go back the oem exhaust connections unless you cut and weld a single pipe.

 

[rac]

Sounds like from what some of you guys are saying there is a preference to longer primary runner lengths, which would be my preference acoustically as well.

You would have to custom fabricate a manifold with that in mind if you didn't want the Walton motor sport manifold. Mine is something in between the Walton and the doc race in terms of runner length and has a lower angle collector, so it's definitely possible to stuff more pipe in there and have smoother collectors. There is space to go down and loop back up . The trick in making it all fit is the down pipe design and planning for it with the primaries and collector positions.

There's is no point starting with a doc race manifold, you need to modify the whole lot.

 

[rac]

Cheers for the replies guys. Either of you have any clips you can share? I’d love to hear what they sound like.

Sorry I don't.

 

[DCTFox]

Sounds like from what some of you guys are saying there is a preference to longer primary runner lengths, which would be my preference acoustically as well.

You would have to custom fabricate a manifold with that in mind if you didn't want the Walton motor sport manifold. Mine is something in between the Walton and the doc race in terms of runner length and has a lower angle collector, so it's definitely possible to stuff more pipe in there and have smoother collectors. There is space to go down and loop back up . The trick in making it all fit is the down pipe design and planning for it with the primaries and collector positions.

There's is no point starting with a doc race manifold, you need to modify the whole lot.

Comparing photos of the two manifolds side by side, I think you’ve hit the nail on the head there mate. That does appear to be the big difference between the two and it makes sense that it would have an effect on the sound emitted. Guess I’ll have to keep this in mind if I ever get a custom kit made!

Thanks everyone for the replies.

 

[DCTFox]

Yes I'am from OZ and we tried everything and the final revised kit is of it tits for big hp.

We just finished 93 tuning and next we are going back to e85 to run some numbers but 500rwk on our low reading dyno
is not a problem.

We ran the car on two completely different dynos and the power levels where almost identical +-5rwk.

I personally run the gc2.0 with the upgraded mar-m246 wheels and they have been solid, I made 387rwk on e15, basically 93 with a splash of e for knock control.

Way to much power for street and track use but if your into drags this can be done of straight e85 and turned up to 450rwk plus with the right supporting mods.

Its way more than any stock engine can handle.

Set a realistic goal and stick to it.

I’m guessing 500rwk is what you expect to get with E85? Otherwise that’s some serious power on 93.
I’m not after any huge hp numbers, somewhere around 400rwk would be ideal. There’s just a lot I like about a single in comparison to upgrading the twins e.g. simplicity, ease of maintenance, reliability, sound, less stress on drivetrain etc.

 

[135i2]

We have almost finished tuning on 98 (93 in the US). So far 405rwkw (Aussie Dyno Dynamics) is max on a 93 base with a splash of E for knock control. Bare in mind everything on my car is optimised to the extreme and I doubt someone with a closer to stock setup will consistently replicate my results.

We have hit just under 500rwkw on Caltex E70 @ 5100rpm with many issues from the car being off the road during fabrication.
It was an old tune from my first Motiv based turbo kit and not good enough to chase power.

There is 600rwkw in my latest tubular manifold kit on a built motor and E85.
We are about to flip over to E85 tuning soon and my built motor is half done already.